1. Field
Various embodiments of the present invention relate to a technology for transmitting and receiving a signal.
2. Description of the Related Art
In general, integrated circuit chips operate while exchanging signals (e.g., data) with peripheral chips. For example, a memory chip such as a DRAM or a flash memory exchanges data with a memory controller, and a central processing unit (CPU) also exchanges data with various chips on a board. Furthermore, signal transmission is not only performed between chips, but it is also performed between internal circuits within an integrated circuit chip.
While signals are transmitted/received, electric current is consumed. The current consumption increases in proportion to the number of transmission lines and the operation frequency. As the data processing ability of an integrated circuit increases, the integrated circuit must transmit/receive more data. Thus, the number of transmission lines and the operation frequency inevitably increase. Therefore, current consumption during signal transmission needs to be reduced.
FIG. 1 illustrates a conventional transmitting/receiving system.
Referring to FIG. 1, the transmitting/receiving system includes a transmitting circuit 110 and a receiving circuit 120.
The transmitting circuit 110 receives an input signal INPUT which swings from a ground voltage VSS (i.e., 0 V) to a power supply voltage VDD, and drives a transmission line 101 with the received signal. The signal swings on the transmission line 101 from the ground voltage VSS to the power supply voltage VDD like the input signal INPUT.
The receiving circuit 120 receives the signal from the transmission line 101 and outputs an output signal OUTPUT which swings from the ground voltage VSS to the power supply voltage VDD.
While a signal is transmitted/received, most of the power is consumed in charging/discharging the transmission line 101. The power consumption at the transmission line 101 may be expressed as the following equation:P=G*f*(signal swing amplitude)2.
In the above equation, ‘P’ represents power consumption, ‘C’ represents capacitance of the transmission line 101, and ‘f’ represents the frequency of a signal transmitted to the transmission line 101.
One method for reducing power consumption during signal transmission is to reduce the swing amplitude of the signals transmitted/received on the transmission line 101. When the swing amplitude of the signal is reduced by ½, the power consumption is reduced to ¼. Thus, such methods exhibit a strong effect on power consumption. However, to reduce the swing amplitude of a signal, a voltage lower other than the power supply voltage VDD must be used, requiring a level shift circuit with a large circuit area. Furthermore, the occurrence of errors may increase due to noise caused in the reduced signal swing amplitude.